(Back to Graywater for gardens) Common practices
Graywater is an excellent source of irrigation for lawns.
Most jurisdictions do not permit aeration of graywater (i.e. cannot use sprinklers). This is to prevent wind transfer of bacteria carrying water to neighboring properties, and potential spreading illness.
To contain the water within the property, under turf irrigation is used. Dripperlines are laid at least 2" under the ground surface, to ensure effective irrigation, and also prevent damage to the dripperlines from mowers etc (dripperlines should be laid deeper if mechanical aeration methods are expected in the future).
Standard dripperlines are placed under the lawn every 12" - 22", with the separation determined by the soil type and lawn characteristics.
To read more about under lawn dripperlines, click here: http://www.irrigray.com/Lawn.html
If you haven't already done so, read our page regarding graywater dripperlines, subsurface dripperlines before reading the rest of this page.
Points to consider when installing under lawn:
Consult a local turf expert to find out how much water your lawn needs. Make sure you mention that you are considering sub surface irrigation, as this is far more water efficient than sprinklers.
Under lawn dripperlines run much slower than above ground IrrigrayTM graywater dripperline. If you were planning to irrigate a 300 sq ft lawn area and no garden beds, the maximum flow rate the lawn dripperline will permit is between 1.5 and 3 gallons per minute.
A single shower can produce 4 gallons per minute or more, and graywater could be lost to overflow unless a larger graywater diversion pumping unit is used (increasing cost).
In many situations a combination of garden bed and lawn area irrigation is used. In these circumstances overflow loss is unlikely.
Until the turf roots have established in the soil, the turf (or seed) must be top watered, via hose or sprinklers. This should only be done with rain water or potable water.
Continue with top watering until sunlight does not reach the soil surface directly. At this stage the turf roots will have sufficient depth to reach the constant moisture zone, and the sun will bake the very top layer of soil.
In areas affected by long term drought, people forget that plants and lawns require fertilization when watered. If your grass is developing a yellow tinge, refer to a local garden nursery for advice, although it is most likely to caused by lack of fertilizer.
Under lawn dripperline requires finer filtration (120 mesh) than IrrigrayTM graywater garden bed dripperline (40 mesh). The Irrigraytm filter is a large capacity 40 Mesh filter while 120 Mesh filters generally use mesh screening to filter - this can clog quickly if used as the primary graywater filter.
Using a high capacity 40 mesh filter first significantly reduces the amount of particulate reaching the second, 120 mesh, filter.
Because of the design of the IrrigrayTM 40 mesh filter, after around 500 gallons of typical graywater has passed through, the particulates trapped in the filter become part of the filter process itself, causing the 40 mesh filter to act as a finer filter. This also reduces the amount of particulate reaching the second filter. Of course when the 40 mesh filter is cleaned it reverts back to 40 mesh performance until particulates collect again.
If you are installing both garden bed (IrrigrayTM) and lawn graywater irrigation, ensure the second filter only processes water destined for the lawn - There is no need for ultra filtered water in the garden bed, so passing all the water through the 120 mesh filter simply increases filter cleaning requirements.
Root intrusion can be a problem in under lawn irrigation if the lawn is irrigated via wet / dry cycles (eg. irrigated twice per week, drying out between sessions). Turf roots will grow in the direction of water IF the soil surrounding the existing roots dries.
To counter this, special dripperline is used, containing emitters designed to resist root intrusion. Chemicals may also be added, either directly to the water via inline dosing systems, or as a inside chemical coating within the dripperline.
Graywater irrigation, however, occurs on a daily basis. The soil maintains a relatively constant moisture level, so the turf roots do not need to grow and seek moisture. Using dripperlines with root intrusion resistant emitters is still recommended as a safeguard, but chemicals are not required (and best avoided for the environment).
We are yet to see any evidence of root intrusion in residential graywater lawn irrigation systems if the above guidance is followed.
Although regulations and recommendations do not permit aeration of graywater, many people still do it.
If you are considering this, reduce the risk of airborne transfer of bacteria by using either a hose with a nozzle that forms large drops, or a dome sprinkler (with the large hole in the middle).
Also consider the following risks:
Soaker hoses are not recommended, as they will quickly clog even if the graywater is filtered via 120 Mesh filters.
Further Information about graywater: